Estimating flap thickness for cochlear implants

ABSTRACT

A flap thickness measurement system includes a reference cochlear stimulation system. The reference cochlear stimulation system includes a sound processor, a transmitter that transmits a telemetric signal, and a cochlear stimulator having a receiver that receives the telemetric signal and transmits a signal back to the transmitter. The system further includes one or more flap simulators having one or more known thicknesses that is positioned between the transmitter and receiver. Also included is a microprocessor that receives and processes data representative of tank voltage from the reference cochlear stimulation system.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/016,604, filed Dec. 16, 2004, to which priority is claimed and whichis incorporate herein by reference in its entirety.

BACKGROUND

The following description relates to cochlear implants, and moreparticularly to fully implantable cochlear implant systems that allowprofoundly deaf persons to hear sounds without the need for wearing orcarrying external hearing devices or components. For such implants, itis useful to estimate the patient's flap thickness around the area ofthe implant (in general, the thickness of the flap of skin on thepatient's skull) using measurements of radiofrequency transferefficiency.

Cochlear implants provide a new mechanism for hearing when a hearing aidis insufficient to overcome a hearing impairment. Advances in cochlearimplants make it possible today for otherwise completely deafindividuals to hear. Unlike a hearing aid that amplifies sound to makeit loud enough for an impaired ear to detect it, a cochlear implantbypasses the damaged part of the anatomy and sends sound signalsdirectly to the auditory nerve, thus restoring the ability to hear soundin an individual who is deaf.

Typical cochlear implant systems today have four components: a soundprocessor; a transmitter; an implant; and an array of electrodes. Thesound processor and transmitter usually reside outside the human body,while the implant and electrodes are surgically implanted in anindividual's head, near the affected ear.

The sound processor can be a small hand-held unit, stored in a pocket orattached to a belt clip, or hung around an individual's ear. Thetransmitter is typically a small unit that transmits informationreceived from the sound processor to the implant. The transmitterusually sends a radiofrequency (RF) signal to the implant through theindividual's skin. The implant receives the information and convertsdigital information into electrical signals, which are sent to theelectrode array.

In many systems today, the transmitter is positioned behind the ear thetransmitter and implant, which attract each other across the skin flapand hold the transmitter in place. Usually, inside of the transmitterthere is a coil that is used to inductively or magnetically couple amodulated AC carrier signal to a similar coil that is included withinthe implant. In order to achieve efficient coupling without sufferingsignificant losses in the signal energy, it is important that theexternal coil within the transmitter be properly aligned with theinternal coil within the implant.

Flap thickness, which is the thickness of the skin and accompanyingtissue between the two magnets, can vary by individual. Flap thicknesscan have an impact on efficient coupling between the transmitter andimplant. Furthermore, flap thickness data is helpful in determining theappropriate strength of the securing magnets. Magnets with too muchstrength can lead to discomfort and necrosis, while magnets with toolittle strength do not secure the transmitter in place. Currentmeasurement techniques for flap thickness include the use of needles andgauss meters, which can be both painful and inconvenient.

SUMMARY

The present inventors recognized a need for determining flap thicknesswith sufficient specificity to enable the design of RF systems that areoptimized for the average patient while still covering the range ofdistances between the transmitter and receiver in the implant, and alsofor determining the optimum magnet strength for any individual.

In one aspect, a method of estimating a thickness of a skin flap of ahuman subject having an implanted cochlear implant includes collectingmeasurement data by performing a plurality of measurements of an amountof electrical energy stored in the cochlear implant while varying astimulation load signal or a power level, or a combination of both,applied to the cochlear implant. The collected measurement data iscompared with predetermined calibration data, and the skin flapthickness is estimated based at least in part on a result of thecomparison.

In another aspect, a method of obtaining reference data for use indetermining flap thickness is described. The method includestransmitting energy at a first power level across a first flap simulatorhaving a first known thickness and obtaining a first set of calibrationdata representative of a first measurement of tank voltage. The methodalso includes transmitting energy at the first power level across asecond flap simulator having a second known thickness different from thefirst known thickness and obtaining a second set of calibration datarepresentative of a second measurement of tank voltage. The method mayalso include transmitting energy at a second power level across thefirst flap simulator and obtaining a third set of calibration datarepresentative of a third measurement of tank voltage, and transmittingenergy at the second power level across the second flap simulator andobtaining a fourth set of calibration data representative of a fourthmeasurement of tank voltage.

In another aspect, a method of obtaining reference data for use indetermining flap includes obtaining two or more measurements of tankvoltage across a flap simulator of a first known thickness, wherein adifferent power level is applied with respect to each measurement. Themethod may further include obtaining two or more measurements of tankvoltage across a flap simulator of a second known thickness, wherein adifferent power level is applied with respect to each measurement.

In another aspect, a method of obtaining reference data for use indetermining flap thickness includes measuring an amount of electricalenergy stored in a cochlear implant using a predetermined stimulationload and a predetermined power level. The method also includes alteringat least one of a stimulation load value and a power level value, andrepeating the electrical energy storage measurement using the at leastone altered value.

In another aspect, a flap thickness measurement system includes areference cochlear stimulation system. The reference cochlearstimulation system includes a sound processor, a transmitter thattransmits a telemetric signal, and a cochlear stimulator having areceiver that receives the telemetric signal and transmits a signal backto the transmitter. The system further includes one or more flapsimulators having one or more known thicknesses that is positionedbetween the transmitter and receiver. Also included is a microprocessorthat receives and processes data representative of tank voltage from thereference cochlear stimulation system.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features and advantages willbe apparent from the description and drawings and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1A illustrates a typical cochlear stimulation system as currentlyused by many patients, including an implantable cochlear stimulator(ICS) that is inductively coupled with an external headpiece (HP)connected with an external speech processor (SP) and power source.

FIG. 1B illustrates a behind-the-ear (BTE) cochlear stimulation systemthat includes an implanted cochlear stimulator (ICS) and an external BTEunit that includes a power source, a speech processor and a microphone.

FIG. 2 is a flow chart depicting a method for obtaining reference datafor use in determining flap thickness.

FIG. 3 is a flow chart depicting a method for obtaining reference datafor use in determining flap thickness in accordance with anotherembodiment.

FIG. 4 is a flow chart depicting a method for estimating flap thicknessfor a cochlear stimulation system.

FIG. 5 is a graph depicting a measurement of an individual's flapthickness plotted against three reference measurements taken at threepower levels.

FIG. 6 is a diagram of one embodiment of an analog-to-digital conversionsystem associated with an implantable cochlear stimulator.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

An overview of an exemplary cochlear stimulation system is providedbelow in connection with FIGS. 1A and 1B. The following description isexemplary and the devices, systems, and methods described herein can beused with other types and other configurations of cochlear stimulationsystems.

A representative cochlear stimulation system of the type currently usedby many patients is fully described, e.g., in U.S. Pat. No. 5,776,172(“the '172 patent”), incorporated herein by reference. As described inthe '172 patent, and as illustrated in FIG. 1A, such existing systemincludes implanted and external components. The external componentsinclude a speech processor (SP), a power source (e.g., a replaceablebattery), and a headpiece (HP) 106. The SP and power source aretypically housed within a wearable unit 102 that is worn or carried bythe patient. The wearable unit is electrically connected to the HP 106via a cable 104. A microphone 107 is also included as part of theheadpiece 106.

The implanted components include an implantable cochlear stimulator(ICS) 112 and an array of electrodes 114. The electrode array 114 isintended for implantation within the cochlear of the patient. The ICS112 is implanted behind the ear, so as to reside near the scalp. Theelectrode array 114 is permanently connected to the ICS by way of amulti-conductor implantable cable 116.

Inside of the headpiece 106 is a coil (transmitter) that is used toinductively or magnetically couple a modulated AC carrier signal to asimilar coil (receiver) that is included within the ICS 112. In order toachieve efficient coupling, without suffering significant losses in thesignal energy, it is important that the external coil within theheadpiece be properly aligned with the internal coil inside the ICS. Toachieve proper alignment, a magnet is typically included within both theheadpiece 106 and the ICS 112, and the resulting magnetic attractionbetween the two magnets not only aligns the coils, as desired, but alsoprovides a holding force that maintains the headpiece 106 securelyagainst the scalp or skin flap 110 of the patient.

In use, a carrier signal is generated by circuitry within the wearableunit 102 using energy derived from the power source within the speechprocessor unit 102. Such carrier signal, which is an AC signal, isconveyed over the cable to the headpiece 106 where it is inductivelycoupled to the coil within the ICS 112. There it is rectified andfiltered and provides a DC power source for operation of the circuitrywithin the ICS 112. Sounds are sensed through the external microphone107, amplified and processed by circuitry included within the speechprocessor unit 102, and converted to appropriate stimulation signals inaccordance with a selected speech processing strategy by circuitrywithin the speech processor unit 102. These stimulation signals modulatethe carrier signal that transfers power to the ICS 112. The ICS includesan appropriate demodulation circuit that recovers the stimulationsignals from the modulated carrier and applies them to the electrodeswithin the electrode array 114. The stimulation signals identify whichelectrodes, or electrode pairs, are to be stimulated, the sequence ofstimulation and the intensity of the stimulation.

Some embodiments of the ICS 112, as indicated in the '172 patent,include a back telemetry feature that allows data signals to betransmitted from the ICS 112 to the headpiece 106, and hence to theSpeech Processor 102. Such back telemetry data provides importantfeedback information to the speech processor regarding the operation ofthe ICS, including the amount of power needed by the ICS. See, e.g.,U.S. Pat. No. 5,876,425, issued to the same assignee as the presentapplication, and also incorporated herein by reference.

When adjustment or fitting or other diagnostic routines need to becarried out, an external programming unit 108 is detachably connected tothe SP unit 102. Through use of the external programmer 108, aclinician, or other medical personnel, is able to select the best speechprocessing strategy for the patient, as well as set other variablesassociated with the stimulation process. See, e.g., U.S. Pat. No.5,626,629, incorporated herein by reference, for a description of arepresentative fitting/diagnostic process.

FIG. 1B depicts a behind-the-ear (BTE) unit 120. The BTE unit 120 mayinclude everything that was previously included within the wearable unit102, only in a much smaller volume. The BTE unit 120 thus includes asuitable power source, as well as the circuitry needed for performing adesired speech processing function. With the BTE unit 120, there is thusno need for the cable 104, and the patient simply wears the BTE unitbehind his or her ear, where it is hardly noticed, especially if thepatient has hair to cover the BTE unit. Advantageously, the batteriesemployed within the wearable unit 102 (FIG. 1A) or the BTE unit 120(FIG. 1B) may be readily replaced when needed.

The present inventors recognized a need to determine the skin flap 110thickness in a noninvasive and convenient manner. Measurements of flap110 thickness enable the design of RF systems for cochlear stimulationsystems that are optimized for the average patient while still coveringthe range of distances between the transmitter in the HP 106 or SP/PWR120 and receiver in the ICS 112.

To obtain reliable measurements estimating flap thickness, reference orcalibration data is first collected prior to obtaining a particularindividual's measurements. FIG. 2 is a flowchart that depicts a methodfor obtaining reference data for use in determining flap thickness. Afirst series of steps for obtaining data representing tank voltagemeasurements associated with a first flap simulator having a knownthickness is shown at 200. A second series of steps for obtaining datarepresenting tank voltage measurements associated with a flap simulatorhaving a known thickness that is different from the flap simulator usedin 200 is shown at 300. A third series of steps for obtaining datarepresenting tank voltage measurements associated with a flap simulatorhaving a known thickness that is different from the flap simulator usedin 200 and 300 is shown at 400. The three series of steps 200, 300 and400 can be performed substantially simultaneously as shown in FIG. 2 orsequentially in any order. Thus, steps 200-280 may be performed prior tosteps 300-380, which may be performed prior to steps 400-480.Alternatively, steps 400-480 may be performed first followed by steps200-280 or 300-380. Alternatively, steps 300-380 may be performed firstfollowed by steps 200-280 or 400-480.

Steps 200-280 will next be discussed. At steps 200-280, a flap simulatorof a known thickness is used to simulate a human flap of skin justbehind the ear. A reference cochlear stimulation system in accordancewith those described herein is used. The flap simulator is placed inbetween a transmitter and receiver of the reference cochlear stimulationsystem. In an implanted cochlear stimulation system, the transmitterwould be secured to the outside of the individual's head and thereceiver would be implanted underneath the skin flap juxtaposed with thetransmitter. In steps 200-280, an implanted cochlear stimulation systemis simulated by placing the flap simulator in between the transmitterand receiver. Energy is transmitted by the transmitter through the flapsimulator to the receiver at a first power level P1 at 210. The energytransmitted can be RF energy or any other type of suitable telemetricenergy. Tank voltage data, which is a measure of transfer efficiency, istransmitted back to the transmitter from the receiver and received by amicroprocessor at 220. The data is stored by the microprocessor at 225.Power is increased at 230 and a corresponding energy transmitted againby the transmitter through the flap simulator to the receiver at 240 ata second power level P2. Tank voltage data is transmitted back to thetransmitter from the receiver and received by the microprocessor at 250.The data is stored by the microprocessor at 255. Power is increasedagain at 260 and a corresponding energy transmitted again by thetransmitter through the flap simulator to the receiver at 270 at a thirdpower level P3. Tank voltage is transmitted back to the transmitter fromthe receiver and received by the microprocessor at 280. The data isstored by the microprocessor at 285. Steps 260-280 can be repeated an nnumber of times with an increase in power each time to collect as muchreference data as is practicable or necessary.

Steps 310-380 can be carried out simultaneously with steps 210-280,before steps 210-280, or after steps 210-280 as shown in FIG. 2. Steps310-380 are identical to steps 210-280 except that the flap simulatorthat is used has a different thickness from the flap simulator used insteps 210-280. The flap simulator can either be thicker than or thinnerthan the flap simulator used in steps 210-280. Altering the distancebetween the transmitter and receiver by altering the thickness of theflap simulator is one way to vary the stimulation load that is applied.In the case where steps 210-280 and 310-380 are performed sequentiallyor at different times, then one flap simulator that has an adjustablethickness can be used for both series of steps, with the thicknessadjusted so that it varies between steps 210-280 and 310-380. Steps360-380 can be repeated an n number of times with an increase in powereach time to collect as much reference data as is practicable ornecessary.

Another way to alter the stimulation load is to vary the current beingapplied in addition to varying the distance. Therefore, rather than onlyaltering the thickness of the flap simulator, steps 310-380 can beperformed under conditions in which the current being applied is variedas well. Thus, steps 310-380 would be identical to steps 210-280 exceptthat an increased or a decreased level of current is applied in additionto using a flap simulator having a thickness that is different from theone used in steps 210-280.

Steps 410-480 can be carried out simultaneously with steps 210-280and/or steps 310-380, before steps 210-280 and/or 310-380, or aftersteps 210-280 and/or 310-380. In other words, the three respectiveseries of steps, 210-280, 310-380, and 410-480 can be carried at anytime with respect to one another as shown in FIG. 2. Steps 410-480 areidentical to steps 210-280 and 310-380 except that the flap simulatorthat is used has a different thickness from the flap simulators used insteps 210-280 and 310-380. Altering the distance between the transmitterand receiver by altering the thickness of the flap simulator is one wayto vary the stimulation load that is applied. In the case where thethree series of steps are performed sequentially or at different times,then one flap simulator that has an adjustable thickness can be used forall three series of steps, with the thickness adjusted so that it variesbetween steps 210-280, 310-380 and 410-480. Steps 460-480 can berepeated an n number of times with an increase in power each time tocollect as much reference data as is practicable or necessary.

Again, another way to alter the stimulation load is to vary the currentbeing applied in addition to altering the thickness of the flapsimulator. Therefore, rather than altering the thickness of the flapsimulator, steps 410-480 can be performed under conditions in which thecurrent being applied is varied as well. Thus, steps 410-480 would beidentical to steps 210-280 and 310-380 except that an increased or adecreased level of current is applied in addition to using a flapsimulator having a thickness that is different from the ones used insteps 210-280 and 310-380.

As shown at steps 225, 255, 285, 325, 355, 385, 425, 455, and 485, tankvoltage data is obtained and stored. This data is later used asreference or calibration data to estimate flap thickness for patient'sthat use implanted cochlear stimulation systems.

The method described in FIG. 2 is one exemplary embodiment of a methodof obtaining reference or calibration data, in which reference data atthree different power levels and three different stimulation loads(i.e., flap simulator thicknesses and/or current levels) are used. Otherembodiments may use as few as two power levels and two stimulation loads(i.e., different flap simulator thicknesses or current levels) or asmany as five, six, seven, eight, nine, ten or n number of power levelsand stimulation loads, with n representing any number above ten.

FIG. 3 represents another method of obtaining reference or calibrationdata. At step 500, a flap simulator of a known thickness is used tosimulate a human flap of skin just behind the ear. As shown in FIG. 3, areference cochlear stimulation system in accordance with those describedherein is used. The flap simulator is placed in between a transmitter(SP & PWR) and receiver (ICS) of the reference cochlear stimulationsystem. In an implanted cochlear stimulation system, the transmitterwould be secured to the outside of the individual's head and thereceiver would be implanted underneath the skin flap juxtaposed with thetransmitter. In steps 500, 600, and 700, an implanted cochlearstimulation system is simulated by placing the flap simulator in betweenthe transmitter and receiver. Energy is transmitted by the transmitterthrough the flap simulator to the receiver at a known and predeterminedpower level. Tank voltage data, which is a measure of transferefficiency, is transmitted back to the transmitter from the receiver andreceived by a microprocessor integrated with the speech processor andpower source (PROG). The data is stored by the microprocessor for lateruse. The microprocessor may alternatively be a standalone computer thatcommunicates directly with the headpiece speech processor and powersource in any manner known to those of skill in the art, such as througha wireless, serial, or parallel connection.

In addition, current can be varied across a predetermined range whilerecording tank voltage data. This can be accomplished in a continuousprocess or a sequential process. In either case, tank voltage data istransmitted, either continuously or sequentially, to the transmitterfrom the receiver and received by the microprocessor. By varying currentwhile measuring tank voltage data, additional data points are gatheredfor later correlation with data received from human subjects who arefitted for cochlear implants and/or cochlear implant magnets.

A difference between steps 500, 600, and 700 is that the flap simulatorhas a different thickness in each step. The flap thickness of the flapsimulator is depicted as increasing from step 500 to 700, with the flapsimulator having the greatest thickness at step 700. Steps 500-700 canbe performed sequentially as shown in FIG. 3, simultaneously, or atdifferent times in random order. If they are performed simultaneously,then three separate flap simulators having three different thicknessescan be used. If they are performed sequentially or at different times,then one flap simulator that has an adjustable thickness can be used forall three steps, with the thickness adjusted so that it varies betweensteps 500, 600, and 700.

Also, any of steps 500-700 can be repeated an n number of times using adifferent power level (i.e., RF strength) each time in a predeterminedrange of power levels so that tank voltage data for different powerslevels and different loads can be collected and used as reference orcalibration data. This can be accomplished in a continuous process or asequential process in which both power level and current are beingvaried while collecting tank voltage data.

FIG. 4 is a flowchart showing steps associated with a method ofestimating flap thickness. The first step, not shown, is to implant acochlear stimulation system, such as anyone of those described herein orincorporated herein by reference. As shown in FIGS. 1A and 1B, animplantable cochlear stimulator 112 is implanted underneath a flap ofskin behind an individual's ear. A headpiece 106 or speech processor andpower source 120 is secured against the individual's head juxtaposedwith the ICS 112 on the outer side of the flap of skin.

After the cochlear stimulation system is in place, at step 800 energy istransmitted at a first known power level by the transmitter associatedwith the headpiece or speech processor and power source across theindividual's flap of skin and to the receiver associated with the ICS onthe other side of the skin flap. Stimulating current transmitted at step800 may also be a known value. Tank voltage data is transmitted back tothe transmitter from the receiver and received by a microprocessor incommunication with the cochlear stimulation system at 810. The tankvoltage data is stored by the microprocessor at 815. The microprocessorcan be a standalone computer that communicates directly with theheadpiece 106 or speech processor and power source 120 in any mannerknown to those of skill in the art, such as through a wireless, serial,or parallel connection. Alternatively, the microprocessor can beintegrated with the headpiece 106 or speech processor and power source120. In either case, the microprocessor either has a display integratedwith it, or communicates with a display. At step 820 energy istransmitted at a second known power level different from the first powerlevel by the transmitter across the individual's skin flap and to thereceiver on the other side of the skin flap. Stimulation current mayalso be a known value that is either the same or different from thestimulation current applied at step 800. Tank voltage data istransmitted back to the transmitter from the receiver and received bythe microprocessor at 830. Tank voltage data is stored by themicroprocessor at 835. At step 840 energy is transmitted at a thirdknown power level different from the first and second power levels bythe transmitter across the individual's skin flap and to the receiver onthe other side of the skin flap. Stimulation current may also be a knownvalue that is either the same as or different from the stimulationcurrent applied at steps 800 and 820. Tank voltage data is transmittedback to the transmitter from the receiver and received by themicroprocessor at 850. Tank voltage data is stored by the microprocessorat 855. The data is correlated with the reference or calibration dataobtained by the processes described above and processed at 860. Anestimate of the thickness of the individual's flap of skin is displayedon a display at 870.

The three power levels transmitted at steps 800, 820, and 840 cancorrespond with the power levels transmitted during the acquisition ofcalibration or reference data, but this is not a strict requirement.Also, steps 800-815, 820-835 and 840-855, may be replicated an n numberof times to obtain an n number of sets of tank voltage data with thepower level changing each time.

In one alternative embodiment, steps 840-855 may be eliminated,consequently obtaining only two sets of tank voltage data to correlatewith reference data. In another alternative embodiment, steps 820-855may be eliminated, consequently obtaining only one set of tank voltagedata to correlate with reference data.

In FIG. 5 the solid lines represent calibration or reference data atthree power levels and one stimulation load. The individual's tankvoltage is plotted with the horizontal lines and the point ofintersection of these lines with the corresponding calibration line isthe estimate flap thickness. Tank voltages that are either too low ortoo high (due to saturation) can be discarded in the estimation.Statistical methods (such as a median) may be used to calculate a value.Ambiguities in the correct result, since there can be two points ofintersection with the calibration data, can be resolved by observing anincrease or decrease in tank voltage with increasing load. Load can beeither distance or stimulation. Increasing tank voltage would indicatethat the lower estimate is correct.

FIG. 6 is a diagram of an implementation of an analog-to-digitalconversion (ADC) system associated with an implantable cochlearstimulator, such as the ICS 112 shown in FIGS. 1A and 1B. The INPUTmultiplexor 910 (“the MUX”) when performing the flap thicknessestimation technique described here, is used to shunt current away fromthe stimulation electrodes 920. In one implementation, the MUX 910 is ananalog multiplexor, but it could be digital instead in otherimplementations. The MUX 910 has the ability, through application ofappropriate control signals 915, to connect together all of its inputsignals and its output signals simultaneously. All of the electrodes,including the stimulation electrodes 920, the stapedius electrodes 930and the indifferent (ground) electrodes 940, which are connected tosignal ground, are substantially simultaneously connected to the outputsof MUX 910, which is connected to an A/D subsystem 950. In oneimplementation, there are a total of twenty input electrodes: sixteenstimulation electrodes 920, two stapedius electrodes 930, and twoindifferent electrodes 940. The impedance to current flow through theMUX 910 to ground 940 is much smaller than the impedance through thestimulation electrodes 920 and tissue and back through the groundelectrodes 940. Therefore, almost all of the current is shuntedinternally to ground so that virtually no current is applied to thestimulation electrodes and thus the patient does not hear thestimulation. This enables the production of fixed loads on a cochlearimplant and the measurement of the transfer function at levels that anindividual would not otherwise be able to tolerate. In oneimplementation, the whole ADC system depicted in FIG. 6 can beimplemented on a single application specific integrated circuit (ASIC).

Other embodiments are within the scope of the following claims.

1. A method of configuring a cochlear implant system, the methodcomprising: collecting individualistic data in a medical implant systemcomprising a medical implant implanted within a user and an externalportion affixed external to the user, wherein the individualistic datacomprises a plurality of measurements indicative of energy received atthe medical implant in response to transmission from the externalportion at a plurality of different powers; comparing the collectedindividualistic data with reference data, wherein reference data isindicative of distances between a transmitter and a receiver in areference medical implant system; and configuring the cochlear implantsystem based at least in part on a result of the comparison.
 2. Themethod of claim 1, wherein configuring the cochlear implant systemcomprises controlling transmission to the cochlear implant.
 3. Themethod of claim 1, wherein comparing the collected individualistic datawith the collected reference data comprises estimating a distancebetween the medical implant and the external portion.
 4. The method ofclaim 1, wherein the measurements indicative of energy received at themedical implant comprise tank voltages.
 5. The method of claim 1,wherein the medical implant comprises a cochlear implant, and whereinthe external portion comprises a speech processor.
 6. The method ofclaim 1, wherein configuring the cochlear implant system comprisesconfiguring the power of signal transmission between the externalportion and the medical implant.
 7. The method of claim 1, whereincomparing the collected individualistic data with reference data occursat a microcontroller associated with the external headpiece.
 8. A methodof configuring a cochlear implant system comprising a cochlear implantimplanted within a user and an external headpiece affixed external tothe user, the method comprising: transmitting a plurality of signalsfrom a transmitter in the external headpiece affixed external to theuser to a receiver in the cochlear implant implanted within the user,wherein each signal comprises a different power; measuring a voltage atthe receiver in response to each signal; and determining a distancebetween the transmitter and the receiver by comparing the measuredvoltages to reference data.
 9. The method of claim 8, wherein thetransmitter and the receiver both comprise a coil.
 10. The method ofclaim 8, wherein the measured voltages are transmitted from the cochlearimplant to the external headpiece.
 11. The method of claim 10, whereinthe measured voltages are processed by a microprocessor associated withthe external headpiece.
 12. The method of claim 8, wherein the measuredvoltages comprise voltages of a tank circuit in the cochlear implant.13. The method of claim 8, wherein the reference data comprises datadefining receiver-to-transmitter distance as a function of transmitterpower and receiver voltage as taken from a reference system.
 14. Themethod of claim 13, wherein the reference system is external to theuser.
 15. The method of claim 13, further comprising as initial steps inthe method, collecting the reference data, comprising: obtaining aplurality of first receiver voltages at a receiver in the referencesystem in response to a plurality of first signals transmitted from atransmitter in the reference system, wherein each first signal comprisesa different power, wherein the first signals are transmitted across afirst flap simulator of a first thickness; and obtaining a plurality ofsecond receiver voltages at the receiver in the reference system inresponse to a plurality of second signals transmitted from thetransmitter in the reference system, wherein each second signalcomprises a different power, wherein the second signals are transmittedacross a second flap simulator of a first thickness different from thefirst thickness.
 16. The method of claim 8, further comprisingconfiguring signal transmission between the transmitter and the receiverbased on the determined distance.
 17. The method of claim 8, wherein thecochlear implant comprises a first magnet and the external headpiececomprises a second magnet attracted by a strength to the first magnet tohold the external headpiece in place relative to the cochlear implant,and further comprising determining the strength of the first and secondmagnets based on the determined distance.
 18. A cochlear implant system,comprising: an external headpiece, comprising a transmitter, and amicroprocessor for storing reference data, wherein the reference datacomprises data indicative of a receiver-to-transmitter distance as takenfrom a reference system, wherein the microprocessor further isconfigured to compare individualistic data received from the cochlearimplant to the reference data to estimate a distance between thetransmitter and the receiver; and a cochlear implant comprising thereceiver, the cochlear implant configured to transmit theindividualistic data to the external headpiece, wherein theindividualistic data comprises a plurality of measurements indicative ofenergy received at the cochlear implant in response to transmission fromthe transmitter at a plurality of different powers.
 19. The system ofclaim 18, wherein the measurements indicative of energy received at thecochlear implant comprise tank voltages.
 20. The system of claim 18,wherein the microprocessor is further configured to configure a power ofsignal transmission between the external portion and the medical implantbased on the estimated distance.
 21. The system of claim 18, wherein thetransmitter and the receiver both comprise a coil.
 22. The system ofclaim 18, wherein the reference system is external to the user.
 23. Thesystem of claim 18, wherein the reference data was procured inaccordance with a method, the method comprising: obtaining a pluralityof first receiver voltages at a receiver in the reference system inresponse to a plurality of first signals transmitted from a transmitterin the reference system, wherein each first signal comprises a differentpower, wherein the first signals are transmitted across a first flapsimulator of a first thickness; and obtaining a plurality of secondreceiver voltages at the receiver in the reference system in response toa plurality of second signals transmitted from the transmitter in thereference system, wherein each second signal comprises a differentpower, wherein the second signals are transmitted across a second flapsimulator of a first thickness different from the first thickness.